JPH0361328B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrolytic capacitor using a novel driving electrolyte. Electrolytic capacitors are made by winding a foil of a valve metal such as aluminum together with a separator to create a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, and the capacitor element is housed in a metal case such as aluminum or a synthetic resin case. It has a sealed structure. [Conventional technology] Conventionally, the driving electrolyte for electrolytic capacitors uses ethylene glycol, etc. as the main solvent.
Generally, an electrolytic solution is used in which about 10% water and a salt, such as an ammonium salt of an organic acid (for example, adipic acid), which does not corrode the valve metal electrode, are dissolved as the electrolyte. (Refer to Japanese Patent Publication No. 58-13019, etc.) However, the above-mentioned electrolytic solution generally has a drawback that tan δ changes greatly in a high-temperature load test (for example, a test at 110° C.) and lacks high-temperature stability. Further, there was a problem in that corrosion occurred due to the halogen ions generated after cleaning with a halogen solvent. The above-mentioned problems have been solved by using amine salts of aromatic carboxylic acids (eg, triethylamine O-phthalate, etc.) and non-aqueous solvents (eg, lactones), which have excellent thermal stability. (Unexamined Japanese Patent Publication 1986)
(Refer to Publications No.-7617, No. 61-82415, etc.) However, it has been impossible to produce a product with a rating of 100V using the above electrolytic solution due to its low withstand voltage. [Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks, improves withstand voltage characteristics without impairing conductivity, and provides an electrolytic capacitor (particularly a rated 100V product) with excellent high temperature stability. The purpose is to provide. [Means for Solving the Problems] The present invention satisfactorily achieves the above object, and the present invention provides tungstic acid, metatungstic acid, and paratungstic acid in a polar organic solvent in which a carboxylic acid or a salt thereof is dissolved. The present invention provides an electrolytic capacitor characterized in that a driving electrolyte containing an acid or a salt thereof is used. Among the above solutes added to the driving electrolyte,
Salts of tungstic acid (H ₂ WO ₄ ), paratungstic acid (12WO ₃・5H ₂ O), or metatungstic acid (H ₂ W ₁₂ O ₄₀・nH ₂ O, n=20-40) are Preferably used. Preferred examples of these salts include ammonium salts, quaternary ammonium salts, amine salts, and alkali metal salts. Among them, ammonium salt of metatungstic acid ((NH ₄ ) ₆ [H ₂ W ₁₂ O ₄₀ ]・nH ₂ O), ammonium salt of paratungstic acid (5
(NH ₄ ) ₂ O.12WO _{3.5H 2} O), sodium tungstate (Na ₂ WO ₄ ), ammonium tungstate, etc. are particularly preferred because they have excellent high temperature stability. The content of these solutes in the polar organic solvent can be selected in various ways, but when the concentration of these tungstic acids or their salts in the organic polar solvent is small, the spark voltage will not be high enough; Even if it is too large, the spark voltage will not rise above a predetermined value. Thus, the content (concentration) of these tungstic acids or their salts in the electrolyte is preferably
0.1 to 10% by weight, especially 0.1 to 5% by weight are suitable. It goes without saying that the dielectric strength (spark voltage) can be improved by adding tungstic acid, metatungstic acid, paratungstic acid, or their salts, but it can also be used in driving electrolytes that already have sufficient dielectric strength. This is preferable because it improves chemical formation properties and has the effect of reducing leakage current. It should be noted that even if there are substances normally added to the driving electrolyte according to the present invention for other purposes (for example, boric acid and its salts, phosphoric acid and its salts, polysaccharides such as mannite, etc.), tungstic acid or its salts It is not affected by the effects of In the present invention, any polar organic solvent that is commonly used in electrolytic capacitors can be used as the polar organic solvent. As preferred solvents, amides, lactones, glycols, sulfur compounds or carbonates can be used. Preferred specific examples include propyl carbonate, dimethylformamide,
N-methylformamide, γ-butyrolactone,
N-methylpyrrolidone, dimethyl sulfoxide,
ethylene cyanohydrin, ethylene glycol,
Mono- or dialkyl ethers of ethylene glycol can be used. Examples of carboxylic acids or salts thereof include glutaric acid,
Aliphatic saturated carboxylic acids such as adipic acid, unsaturated carboxylic acids such as maleic acid, fumaric acid, itaconic acid, or their ammonium salts, quaternary ammonium salts, amine salts, alkali metal salts, etc. are preferably used, but in particular , fatty acids with a total carbon number of 12 or less or their amine salts are highly effective. Furthermore, aromatic carboxylic acids such as benzoic acid, phthalic acid, and salicylic acid, or their ammonium salts, quaternary ammonium salts, amine salts, alkali metal salts, etc. are preferably used, and in particular, amine salts of aromatic carboxylic acids, Quaternary ammonium salts are preferred. In addition, fluorinated carboxylic acids such as perfluoroadipic acid and fluorobenzoic acid, or their ammonium salts, quaternary ammonium salts, amine salts, alkali metal salts, etc., are also used, especially amine salts of perfluoroadipic acid. , quaternary ammonium salts are preferred. In addition, these carboxylic acids or their salts are contained in a polar organic solvent in an amount of 3 to 70% by weight, more preferably 5 to 60% by weight.
It is preferable to contain it. In the present invention, the content of water in the electrolyte is not necessarily essential, but it is preferable if the electrolyte contains water because it can further reduce the specific resistance, but if it is made too large, the internal pressure of the capacitor at high temperature or cause electrode corrosion. The water content is thus preferably between 0.1 and 10% by weight, especially between 0.5 and 5% by weight. The electrolytic capacitor of the present invention includes various types of capacitors. In a typical embodiment, an aluminum foil anode and an aluminum foil cathode separated by a suitable spacer such as paper are used, these are wound into a cylindrical shape to form a capacitor element, and this element is impregnated with a driving electrolyte. . The amount of electrolyte impregnated with respect to the separator is preferably 50~
It is said to be 300% by weight. The element impregnated with electrolyte is
It is housed in a case made of corrosion-resistant metal or synthetic resin, and has a sealed structure. The present invention will be further explained below using specific examples showing preferred embodiments of the present invention. Note that the present invention should not be construed as being limited by the above description and examples, and various changes can be made within the scope of the present invention. For example, in the case of tungstate salts, substances that form these may be added separately to the driving electrolyte used in the present invention, and if necessary, within a range that does not impede the purpose of the present invention. It is of course possible to dissolve other substances, for example acids such as maleic acid, formic acid, or salts thereof. [Examples] The present invention will be specifically explained based on Examples and Comparative Examples. Using the driving electrolytes having the compositions shown in Comparison 1 to 2 and Examples 1 to 11, the rated voltage was 100V-
A 100μF electrolytic capacitor was manufactured, and its specific resistance (conductivity) and spark voltage were measured and are shown in Table 1. Next, this electrolytic capacitor was subjected to a high-temperature load test at a temperature of 110°C, and changes in tan δ and leakage current at the initial stage and after 1000 hours were measured. The results are shown in Table 1. Weight% Comparative example 1 Ammonium adipate 10 Water 10 Ethylene glycol 80 Comparative example 2 Triethylamine phthalate salt 20 γ-butyrolactone 80 Example 1 Triethylamine phthalate salt 20 Tungstic acid 1 Water 2 Ethylene glycol 38 γ-butyrolactone 39 Example 2 Benzoic acid Acid ammonium salt 12 Ammonium metatungstate 1 Water 3 Ethylene glycol 84 Example 3 Tetramethylammonium maleate 10 Ammonium paratungstate 1 Water 3 γ-butyrolactone 86 Example 4 Trimethylamine glutaric acid salt 13 Ammonium metatungstate 1 Water 2 Ethylene glycol monomethyl ether 14 Propyl carbonate 70 Example 5 O-fluorobenzoic acid triethylamine salt 17 Sodium tungstate 1 Water 2 Ethylene cyanohydrin 40 Sulfolane 40 Example 6 Perfluoroadipate triethylamine salt 20 Ammonium metatungstate 1 Water 2 Ethylene glycol 17 γ-Butyrolactone 60 Example 7 Tetramethylammonium phthalate 15 Ammonium metatungstate 1 Water 3 Boric acid 2 Mannite 3 Ethylene glycol dimethyl ether 16 γ-Valerolactone 60 Example 8 Tetramethylammonium benzoate 15 Ammonium paratungstate 1 Water 2 Ammonium phosphate 0.5 Dimethyl sulfoxide 21.5 Dimethylformamide 60 Example 9 Salimethyl acid trimethylamine salt 15 Ammonium metatungstate 1 Water 2 Ethylene glycol 22 γ-butyrolactone 60 Example 10 Perfluoroadipic acid trimethylamine salt 16 Ammonium tungstate 1 Water 3 Ethylene glycol 40 Dimethylformamide 40 Example 11 Triethylamine maleate 15 Ammonium metatungstate 1 Water 2 Ethylene glycol 22

[Table] [Effects of the invention] Compared to conventional capacitors, the electrolytic capacitor using the electrolyte of the present invention has improved withstand voltage characteristics (spark voltage) and reduced leakage current without reducing conductivity. can. As a result, the working voltage (rated)
This makes it possible to increase the voltage from the conventional 63V to 100V, and at the same time provides an electrolytic capacitor with good characteristics and high temperature stability.

Claims (1)

[Claims] 1. A driving electrolytic solution is used, which is made by adding tungstic acid, metatungstic acid, paratungstic acid, or a salt thereof to a polar organic solvent in which a carboxylic acid or a salt thereof is dissolved. Electrolytic capacitor. 2 0.1 to 5.0% by weight of tungstic acid, metatungstic acid, paratungstic acid, or its salt in a polar organic solvent in which carboxylic acid or its salt is dissolved.
An electrolytic capacitor according to claim 1 contained herein. 3. The electrolytic capacitor according to claim 1 or 2, wherein the salt of tungstic acid, metatungstic acid, or paratungstic acid is an ammonium salt, a quaternary ammonium salt, an amine salt, or an alkali metal salt.